Tuning-fork-type piezoelectric vibrating reed and tuning-fork-type piezoelectric vibrator

ABSTRACT

A tuning-fork-type piezoelectric resonator element and a tuning-fork-type piezoelectric resonator are provided. The tuning-fork-type piezoelectric resonator element comprises a piezoelectric resonator element body including base and resonating arms extending from one end of base. A support includes a short side connected to the base and a long side extending from one end of the short side along a longitudinal direction of the piezoelectric resonator element body. A mount is provided at the tip of the long side and at the short side.

RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2003-139208 filed May 16, 2003 which is hereby expressly incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a tuning-fork-type piezoelectricresonator element and a tuning-fork-type piezoelectric resonator, andmore particularly to a tuning-fork-type piezoelectric resonator elementand a tuning-fork-type piezoelectric resonator, which are suitable forminiaturizing and thinning a tuning-fork-type piezoelectric resonator.

2. Description of the Related Art

A piezoelectric resonator, particularly, a tuning-fork-typepiezoelectric resonator is known as a piezoelectric resonator that canobtain an accurate clock frequency simply and easily. Recent demands tominiaturize and thin electronic devices require a tuning-fork-typepiezoelectric resonator to be miniaturized and thinned. To meet such ademand, a surface mounting type tuning-fork-type piezoelectric resonatorhas been developed. The tuning fork piezoelectric resonator of thissurface mounting type is mounted so that the surface of atuning-fork-type piezoelectric resonator element is made parallel to thebottom face of a package, and the tuning-fork-type piezoelectricresonator element is mounted at the bottom face of the package in theform of a cantilever.

Further, the technique of mounting a tuning-fork-type piezoelectricresonator in a package is disclosed in Japanese Unexamined PatentApplication Publication No. 2001-332952. In Japanese Unexamined PatentApplication Publication No. 2001-332952, the tuning-fork-typepiezoelectric resonator element is mounted in the package including apackage base and a cover in the form of a cantilever. Also, a concaveportion having a rectangular shape in a plan view is provided at thepackage base adjacent to resonating arms of the tuning-fork-typepiezoelectric resonator element. The provision of the concave portionallows a free end of the tuning-fork-type piezoelectric resonatorelement to enter the package base without contact therewith, even thoughthe resonator element vibrates greatly due to an external shock. As aresult, the tuning-fork-type piezoelectric resonator element is notdeformed and the frequency characteristics are prevented from beingchanged.

In addition, another mounting method includes the technology disclosedin Japanese Unexamined Patent Application Publication No. 56-61820. InJapanese Unexamined Patent Application Publication No. 56-61820, a frameis provided at a tuning-fork-type piezoelectric resonator element tosurround a tuning-fork-type piezoelectric resonator body. Thetuning-fork-type piezoelectric resonator element is interposed betweentwo packages, which are joined to each other and sealed by metalmaterial. At this time, the joining and sealing are made with the frameprotruding farther than the package. The protruding part of the framefunctions to prevent the metal material provided at upper and lowersides of the frame from being short-circuited.

Meanwhile, in the conventional tuning-fork-type piezoelectric resonator,the tuning-fork-type piezoelectric resonator element is mounted via abase in the form of a cantilever. However, since the tuning-fork-typepiezoelectric resonator element is mounted on the base in the form of acantilever, the parallelism of the tuning-fork-type piezoelectricresonator element mounted inside the package becomes lowered, and thetuning-fork-type piezoelectric resonator element is slantingly mountedtherein. Therefore, the conventional tuning-fork-type piezoelectricresonator has a problem in that the resonating arms may come in contactwith the bottom face of the package or the cover, thereby stoppingoscillation.

Moreover, in the conventional tuning-fork-type piezoelectric resonatordescribed in Japanese Unexamined Patent Application Publication No.2001-332952, in order to prevent the resonating arms from contactingwith the bottom face of the package, a concave portion is formed at thebottom face of the package. The concave portion should have enough depthto reliably prevent the contact of the resonating arms with the package,and thinning the tuning-fork-type piezoelectric resonator becomesdifficult. Furthermore, a base on which the resonating arms of thetuning-fork-type piezoelectric resonator protrude is mounted on thepackage base, causing the problem of increasing vibrating leakage and acrystal impedance (CI) value.

Furthermore, in the conventional tuning-fork-type piezoelectricresonator described in Japanese Unexamined Patent ApplicationPublication No. 56-61820, when two electrodes of the tuning-fork-typepiezoelectric resonator element and a package-side mounting electrodeare electrically connected to one another by a conductive adhesive, thetwo electrodes of the tuning-fork-type piezoelectric resonator elementand the package-side mounting electrode approach each other. Thus, theconductive adhesive may overflow, causing short-circuiting between theelectrodes.

The present invention has been made to solve the above-mentionedproblems, and it is an object of the present invention to provide atuning-fork-type piezoelectric resonator element capable of beingmounted in a package while keeping the parallelism thereof. It isanother object of the present invention to provide a tuning-fork-typepiezoelectric resonator that can be thinned using the tuning-fork-typepiezoelectric resonator element.

SUMMARY

In order to achieve the above objects, the present invention provides atuning-fork-type piezoelectric resonator element comprising: apiezoelectric resonator element body including a base and resonatingarms extending from one end of the base; a support including a shortside connected to the base and formed along the other end of the base,and a long side extending from an end of the short side in thelongitudinal direction of the piezoelectric resonator element body; andmounts provided at the tip of the long side and at the tip of the shortside.

Since the support of the tuning-fork-type piezoelectric resonatorelement is formed along another end of the base and the one long side ofthe piezoelectric resonator element body, the tuning-fork-typepiezoelectric resonator element has a smaller outside dimension than theconventional tuning-fork-type piezoelectric resonator element surroundedby a frame in four directions. As a result, the size of a package formounting the tuning-fork-type piezoelectric resonator element thereincan be reduced. Further, a mount is provided at the short side and attip of the long side to be joined to a package. The mount allows thetuning-fork-type piezoelectric resonator element to be horizontallymounted relative to the bottom face of the package.

Further, it is preferable that the long side extends from one end of theshort side. As a result, the tuning-fork-type piezoelectric resonatorelement can have a smaller outside dimension than that the conventionaltuning-fork-type piezoelectric resonator element surrounded by a framein four directions, and the size of a package for mounting thetuning-fork-type piezoelectric resonator element can be reduced.Moreover, the number of tuning-fork-type piezoelectric resonatorelements, which are obtained from one piezoelectric wafer, can beincreased.

Further, it is preferable that the long side is shorter than thepiezoelectric resonator element body. As a result, the tuning-fork-typepiezoelectric resonator element can have a smaller outside dimensionthan the conventional tuning-fork-type piezoelectric resonator element.Therefore, the number of tuning-fork-type piezoelectric resonatorelements, which are obtained from one piezoelectric wafer, can beincreased.

The support includes a long side formed to extend from one end of theshort side, and a second short side formed at the front end of the longside to face the short side, and the support has a U-shape. As a result,the tuning-fork-type piezoelectric resonator element can have a smalleroutside dimension than the conventional tuning-fork-type piezoelectricresonator element surrounded by a frame in four directions. Also, thenumber of tuning-fork-type piezoelectric resonator elements, which areobtained from the one piezoelectric wafer, can be increased.

Further, the present invention provides a tuning-fork-type piezoelectricresonator comprising: the aforementioned tuning-fork-type piezoelectricresonator element, which is mounted in a package by the mounts; and acover joined to an upper portion of the package. The tuning-fork-typepiezoelectric resonator element can be horizontally mounted relative tothe bottom face of the package. As a result, when the tuning-fork-typepiezoelectric resonator element oscillates, the resonating arms are notbrought in contact with the package. Thus, it is possible to reduce thethickness of the tuning-fork-type piezoelectric resonator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a tuning-fork-type piezoelectric resonatoraccording to a first embodiment.

FIG. 2 is a cross-sectional view of the tuning-fork-type piezoelectricresonator according to the first embodiment.

FIGS. 3 a and 3 b are views illustrating the number of tuning-fork-typepiezoelectric resonator elements according to the first embodiment froma piezoelectric wafer.

FIG. 4 is a plan view of a tuning-fork-type piezoelectric resonatorelement according to a second embodiment.

FIG. 5 is a view illustrating the number of tuning-fork-typepiezoelectric resonator elements according to the second embodiment ofthe present invention obtained from a piezoelectric wafer.

FIG. 6 is a view showing a modified example of the tuning-fork-typepiezoelectric resonator element according to the second embodiment.

FIGS. 7 a–7 d are views illustrating a shape of a tuning-fork-typepiezoelectric resonator element according to a third embodiment.

DETAILED DESCRIPTION

Hereinafter, a tuning-fork-type piezoelectric resonator element and atuning-fork-type piezoelectric resonator according to the presentinvention will be explained. Further, the following description is justone aspect of the present invention, and the present invention is notlimited thereto.

First, a first embodiment of the present invention will be described.FIG. 1 is a plan view of a tuning-fork-type piezoelectric resonator, andFIG. 2 is a cross-sectional view of the tuning-fork-type piezoelectricresonator. A tuning-fork-type piezoelectric resonator 10 is configuredsuch that a tuning-fork-type piezoelectric resonator element 20 ismounted inside a package 12 and the upper part of the package 12 ishermetically sealed with a cover 14.

The tuning-fork-type piezoelectric resonator element 20 includes apiezoelectric resonator element body 26 and a support 28. Thepiezoelectric resonator element body 26 includes a base 22 and a pair ofresonating arms 24 extending from one end of the base 22. The support 28includes a short side 30 formed along another end of the base 22opposite the arms 24 and a long side 32 extending from one end of theshort side 30 along a long side of the piezoelectric resonator elementbody 26. The support 28 has an L shape formed by the short side 30 andthe long side 32. The short side 30 is also connected to the other endof the base 22. The width of the connecting part is narrowed by a pairof cut grooves 34 formed at both sides thereof so that the vibrationleak of the piezoelectric resonator element body 26 is reduced.

In summary, the support 28 is L-shaped and includes a first or short leg30 connected to substantially orthogonally extending second or long leg32. The long leg 32 extends along the resonating arms 24. A base 22 ofthe reed body 26 is connected to the short leg 30 by a relatively narrowconnecting part which is formed by grooves cut between the short leg 30and the base 22.

Further, connection electrodes (not shown) are provided at the bottomface of the short side 30 and at the bottom face on the tip of the longside 32, respectively, so that they are electrically connected toexcitation electrodes (not shown) formed at the resonating arms 24. Theconnection electrodes function as a mount when they are mounted in thepackage 12. Moreover, a mounting alignment pattern 36 is formed at thelong side 32. The mounting alignment pattern 36 is provided to improvelocation accuracy when mounting the tuning-fork-type piezoelectricresonator element 20 in the package 12. Similar to the excitationelectrodes, the mounting alignment pattern 36 is formed of a metal thinfilm or the like.

The package 12 has a box-like shape. The package 12 is configured suchthat the cover 14 formed of glass, ceramic or metal is joined to thepackage base 16 formed of a ceramic insulating substrate or the like viathe sealing portion 38 made of low-melting glass. Package-side mountingelectrodes 18 a and 18 b are formed inside the package base 16 so as tomount the tuning-fork-type piezoelectric resonator element 20. Thepackage-side mounting electrodes 18 a and 18 b are formed correspondingto the connection electrodes that are provided at the short side 30 andthe long side 32 of the tuning-fork-type piezoelectric resonator element20. Particularly, the package-side mounting electrode 18 b correspondingto the connection electrode of the long side 32 is formed only under thelong side 32, but is not formed under the resonating arms 24.Accordingly, since the resonating arms 24 are not in contact with thepackage-side mounting electrode 18 b, the tuning-fork-type piezoelectricresonator element 20 oscillates. A sealing hole 40 is provided at thebottom of the package base 16 and is used when sealing the package 12under vacuum. When mounting the tuning-fork-type piezoelectric resonatorelement 20 in the package 12, the connection electrodes provided at theshort side 30 and the long side 32 and the package-side mountingelectrodes 18 a and 18 b are bonded to each other by a conductiveadhesive 42.

According to the above-mentioned embodiment, since the tuning-fork-typepiezoelectric resonator element 20 is bonded by the connectionelectrodes formed at the short and long sides 30 and 32, and thepackage-side mounting electrodes 18 a and 18 b, the reed 20 can behorizontally mounted relative to the bottom face of the package 12(i.e., parallel to the bottom face). Therefore, when thetuning-fork-type piezoelectric resonator element 20 oscillates, it ispossible to reduce the size of the cavity without the resonating arms 24contacting the cover 14 and the bottom face of the package base 16.Further, it is not necessary to provide the conventionally requiredconcave portion in the package base 16. Accordingly, it is possible tomake the tuning-fork-type piezoelectric resonator 10 thin.

Further, the tuning-fork-type piezoelectric resonator element 20 havingan L-shaped support 28 has a smaller outside dimension than that of theconventional tuning-fork-type piezoelectric resonator element surroundby a frame in four directions. Therefore, the package 12 for mountingthe tuning-fork-type piezoelectric resonator element 20 therein can beminiaturized. Moreover, the tuning-fork-type piezoelectric resonatorelement 20 has a smaller outside dimension that that of the conventionaltuning-fork-type piezoelectric resonator element. Thus, the number oftuning-fork-type piezoelectric resonator elements 20 obtained from onepiezoelectric wafer, can be increased. FIG. 3 is a view illustrating thenumber of obtained tuning-fork-type piezoelectric resonator elements 20.

FIG. 3( a) shows a pattern of tuning-fork-type piezoelectric resonatorelements, surrounded by a frame in four directions, on a piezoelectricwafer. FIG. 3( b) shows the pattern of the tuning-fork-typepiezoelectric resonator elements 20, having the L-shaped support 28, ona piezoelectric wafer. When the tuning-fork-type piezoelectric resonatorelements 20 are patterned at equal intervals and the obtained number ofconventional tuning-fork-type piezoelectric resonator elements is 100,the obtained number of tuning-fork-type piezoelectric resonator elements20 each having the support 28 becomes 145. As a result, 45% moretuning-fork-type piezoelectric resonator elements 20 can be obtainedfrom one piezoelectric wafer than the conventional tuning-fork-typepiezoelectric resonator elements.

Next, a second embodiment will be described. In the second embodiment,tuning-fork-type piezoelectric resonator element will be described. FIG.4 is a plan view of a tuning-fork-type piezoelectric resonator element50 according to the second embodiment. A tuning-fork-type piezoelectricresonator element 50 is the same as the tuning-fork-type piezoelectricresonator element 20 according to the first embodiment except that thelength of a long side 53 is different from that of the long side 32.

The tuning-fork-type piezoelectric resonator element 50 includes apiezoelectric resonator element body 58 having a pair of resonating arms56 extending from one end of a base 54, and a support 51 having a shortside 52 and a long side 53 along another end of the base 54 and a longside 53 extending from one end of the short side 52 along a long side ofthe piezoelectric resonator element body 58. The long side 53 is shorterthan a long side of the piezoelectric resonator element body 58, and,for example, the length of the long side 53 is half that of the longside of the piezoelectric resonator element body 58.

Connection electrodes (not shown) are provided at the bottom face of theshort side 52 and at the bottom face on the tip of the long side 53,respectively. The connection electrodes functions as a mount when theyare mounted in a package.

Moreover, a mounting alignment pattern may be formed at the long side 53of the tuning-fork-type piezoelectric resonator 50.

Since the tuning-fork-type piezoelectric resonator element 50 is bondedto the inside of a package through the mount, it can be horizontallymounted relative to the bottom face of the package. Therefore, when thetuning-fork-type piezoelectric resonator element 50 oscillates, it ispossible to reduce the size of the cavity without the resonating arms 56contacting the cover and the bottom face of the package base. Further,it is not necessary to provide the conventional concave portion in thepackage base. Accordingly, it is possible to make the tuning-fork-typepiezoelectric resonator thin. Moreover, the tuning-fork-typepiezoelectric resonator element 50 has a smaller outside dimension thanthat of the conventional tuning-fork-type piezoelectric resonatorelement surrounded by a frame in four directions. Therefore, the packagefor mounting the tuning-fork-type piezoelectric resonator element 50 canbe miniaturized.

Further, the support 51 provided at the tuning-fork-type piezoelectricresonator element 50 has a smaller outside dimension because it isprovided along another end of the base 54 and a part of the long side ofthe piezoelectric resonator element body 58. Therefore, the number oftuning-fork-type piezoelectric resonator elements 50 obtained from onepiezoelectric wafer can be increased. FIG. 5 is a view illustrating thenumber of tuning-fork-type piezoelectric resonator elements 50 obtainedfrom a piezoelectric wafer. When a pattern is formed by alternatelyarranging the tuning-fork-type piezoelectric resonator elements 50 onthe piezoelectric wafer, the number of tuning-fork-type piezoelectricresonator elements 50 installed on one piezoelectric wafer becomes 177.

The obtained number of the conventional tuning-fork-type piezoelectricresonator elements surrounded by a frame in four directions is 100. As aresult, 77% more of the tuning-fork-type piezoelectric resonatorelements 50 are obtained from one piezoelectric wafer than theconventional tuning-fork-type piezoelectric resonator elements.

In addition to the above-described shape of the support 51, a support 61may be provided along both short sides and one long side of thepiezoelectric resonator element body 58. FIG. 6 is a plan view of atuning-fork-type piezoelectric resonator element having a support 61.The support 61 includes a first short side 62 formed along one end of abase 54, a long side 63 extending from one end of the first short side62, and second short side 64 provided at the front end of the long side63 to face the first short side 62, which forms a U shape.

The same effects as those of the first embodiment can be obtained by theabove construction. That is, when a tuning-fork-type piezoelectricresonator element is mounted in a package, it can be horizontallymounted relative to the bottom face of the package, which leads to areduced size cavity. Accordingly, it is possible to make thetuning-fork-type piezoelectric resonator thin. Moreover, it is possibleto decrease the outside dimension of the tuning-fork-type piezoelectricresonator element as compared with the conventional tuning-fork-typepiezoelectric resonator element surrounded by a frame in fourdirections.

Next, a third embodiment will be described. In the third embodiment, atuning-fork-type piezoelectric resonator element will be described. FIG.7 is a view illustrating shapes of tuning-fork-type piezoelectricresonator elements according to a third embodiment, wherein FIGS. 7( a)to 7(d) show modified examples of the support.

As shown in FIG. 7( a), a piezoelectric resonator element body 73 of atuning-fork-type piezoelectric resonator element 70 a includesresonating arms 72 extending from one end of a base 71. A support 74includes a short side 75 along another end of the base 71, and longsides 76 extending from both ends of the short side 75 in thelongitudinal direction of the piezoelectric resonator element body 73.Further, as shown in FIG. 7( b), a tuning-fork-type piezoelectricresonator element 70 b includes a piezoelectric resonator element body73 and a support 77. The support 77 includes a short side 78 alonganother end of the base 71, and long sides 79 extending from both endsof the short side 78 in the longitudinal direction of the piezoelectricresonator element body 73. Each of the long sides 79 is shorter inlength than a long side of the piezoelectric resonator element body 73.For example, each length of the long sides 79 is half that of the longside of the piezoelectric resonator element body 73. When thetuning-fork-type piezoelectric resonator elements 70 a and 70 b aremounted in a package, the bottom faces of the short sides 75 and 78, andthe bottom faces at both ends of the two long sides 76 and 79 are joinedto the package by a conductive adhesive, so that the tuning-fork-typepiezoelectric resonator elements 70 a and 70 b can be mounted in apackage while being kept horizontal (parallel) to the bottom face of thepackage.

Further, as shown in FIG. 7( c), a tuning-fork-type piezoelectricresonator element 80 a includes a piezoelectric resonator element body83 and a support 84. The piezoelectric resonator element body 83includes a base 81 and resonating arms 82. The support 84 is providedalong long sides at both sides of the piezoelectric resonator elementbody 83, and is connected to the piezoelectric resonator element body 83through a connecting portion 85.

Moreover, as shown in FIG. 7( d), a tuning-fork-type piezoelectricresonator element 80 b is the same as the tuning-fork-type piezoelectricresonator element 80 a except that a support 86 is different in lengthfrom the support 84. That is, the support 86 is shorter than a long sideof the piezoelectric resonator element body 83, and for example, thelength of the support 86 is half that of the piezoelectric resonatorelement body 83. When the tuning-fork-type piezoelectric resonatorelements 80 a and 80 b are mounted in a package, both bottom faces atboth ends of the supports 84 and 86, i.e., four portions of the supports84 and 86 are joined by a conductive adhesive, so that thetuning-fork-type piezoelectric resonator elements 80 a and 80 b aremounted in a package while being kept horizontal (parallel) to thebottom face of the package.

1. A tuning-fork-type piezoelectric resonator element comprising: apiezoelectric resonator element body including: a base; and resonatingarms extending from one end of the base; a support including a short legwhich is connected to a second end of the base opposite the resonatingarms, and a long leg extending from an end of the short leg in alongitudinal direction of the piezoelectric resonator element body; andmounts provided at a tip end of the long leg and at a tip end of theshort leg; wherein the long leg is shorter than the piezoelectricresonator element body.
 2. The tuning-fork-type piezoelectric resonatorelement according to claim 1, wherein the long leg extends from one endof the short leg.
 3. A tuning-fork-type piezoelectric resonator elementcomprising: a piezoelectric resonator element body including: a base;and resonating arms extending from one end of the base; a supportincluding a short leg which is connected to a second end of the baseopposite the resonating arms, and a long leg extending from an end ofthe short leg in a longitudinal direction of the piezoelectric resonatorelement body; and mounts provided at a tip end of the long leg and at atip end of the short leg; a second short leg provided at the free end ofthe long leg; wherein the support has a U-shape with the long legextending between the short leg and the second short leg.
 4. Atuning-fork-type piezoelectric resonator comprising: thetuning-fork-type piezoelectric resonator element according to claim 1mounted in a package by the mounts; and a cover joined to an upperportion of the package.
 5. A tuning-fork-type piezoelectric resonatorelement comprising: a piezoelectric resonator element body including: abase; and a pair of laterally spaced apart resonating arms extendingsubstantially in parallel from one end of the base; a support including:a first leg connected to a second end of the base opposite theresonating arms by a relatively narrow connecting part; and a second legextending substantially orthogonally from a first end of the first leg,the second leg being spaced apart from and projecting substantiallyparallel to the resonating arms; a first mount provided at an end of thesecond leg opposite the first leg; and a second mount provided at asecond end of the first leg opposite the second leg.
 6. Atuning-fork-type piezoelectric resonator element comprising: apiezoelectric resonator element body including: a base; and a pair oflaterally spaced apart resonating arms extending substantially inparallel from one end of the base; an L-shaped support including: afirst leg; and a second leg extending substantially orthogonally from afirst end of the first leg; a first mount provided at an end of thesecond leg opposite the first leg; and a second mount provided at an endof the first leg opposite the second leg; wherein the piezoelectricresonator element body is connected to the first leg by a relativelynarrow connecting part, and the second leg projects substantiallyparallel to the resonating arms.